1. Field of the Invention
The invention relates to the construction industry and, in particular, concerns a method of interconnecting building members to anchor structures.
2. Description of the Related Art
In typical residential and light industrial/commercial building frame wall construction, load bearing frame walls are comprised of a series of studs and posts that are anchored to the foundation and covered with sheathing material installed over both sides of the frame. Typically, the frame is constructed from a number of vertically extending studs that are positioned between and interconnected with upper and lower plates. The lower plates and/or vertical studs are typically anchored to the foundation in some fashion. The covering material, plywood, sheet rock, siding, plaster, etc. is then attached over the studs.
Natural forces commonly occur that impose vertical and horizontal forces on the structural elements of the buildings. These forces can occur during earth movement in an earthquake and from high wind conditions such as hurricanes, tornadoes, cyclones, or other extreme weather conditions. If these forces exceed the structural capacity of the building, they can cause failures leading to damage to or the collapse of the building with resultant economic loss and potential injuries and loss of life.
A typical method of securing a frame to a foundation is to connect one end of a length of metal strapping to an end of wall stud and to embed the other end in the concrete foundation. Uplift forces acting on the building frame are resisted through the embedded strap. The use of metal strapping is convenient to install, but has strength limitations to inhibit uplift. In particular, the metal strapping is typically attached to a frame member such as a post using relatively few fasteners. Thus, each of the fasteners are subjected to a relatively large fraction of the transferring force, increasing the likelihood of the fastener or its attachment points failing.
Another need in existing construction materials and techniques arises with respect to the vertical loads carried by a building's frame. The gravity weight of a building and its contents direct a vertical load that is typically transferred to and carried by the vertical load bearing studs or posts of the building's frame. These vertical members typically bear at their lower end on a pressure treated mudsill.
A mudsill typically comprises a number of 2×4 pieces of lumber placed directly on a foundation so as to lay on the face defined by the 4″ dimension and the longest dimension. A mudsill is also used as a nailing surface along the lower extent of the exterior walls. The inherent structural problem with the mudsill, comprising a wooden member, is that it has less capacity to resist crushing because of the orientation of the grain of the wood. A compressive distortion in the mudsill allows the vertical load-bearing studs to move downwards due to the incident vertical load. Compressive movement of the vertical end studs in a shear panel creates deflection in the walls of the building, weakening the overall structure, providing impetus for cracks to form in the external and interior wall finishings, and potentially concentrating load stresses in unforeseen and damaging ways.
Furthermore, devices that fasten vertical members such as posts to the foundation do so in a substantially rigid manner. In certain force situations, having a substantially rigid and strong interconnection of the post to the foundation may lead to failures at another location.
From the foregoing, it can be appreciated that there is a continuing need for a method and device to continuously secure and anchor a building frame to a foundation. The desired anchoring method should be convenient to install, yet offer strength advantages to the existing use of metal strapping. It would be an additional advantage for the device to be capable of supporting vertical compression loads as well as tension loads to thereby enable the device to transfer loads directly to the foundation. There is a need for an attachment apparatus that permits use of ductile elements so as to allow the attachment apparatus to dissipate a portion of the tension or compression loads, while transferring the rest to the foundation.